QGraphicsView用来显示一个滚动视图区的QGraphicsScene内容。QGraphicsScene提供了QGraphicsItem的容器功能。通常与QGraphicsView一起使用来描述可视化图形项目。
QGraphicsScene提供了一个视图的场景，通过在这样一个场景之上加入不同的QGraphicsItem来构建视图。而QGraphicsView则提供了一个widget来显示QGraphicsScene的内容。所以要想成功构建一个视图，这三个元素缺一不可。
以下是一个QGraphicsView的例子，实现滑动的窗体效果，工具栏和图片均为场景中的Item。
#include <QtCore>
#include <QtGui>
#include <QtSvg>
/*程序中用到了svg格式的图片，所以需包含QtSvg*/
#define PAGE_COUNT 5
/*定义滑动窗体的窗体数*/
定义工具栏，NviBar继承自QGraphicsRectItem，用法与QGraphicsItem类似。
class NaviBar : public QObject, public QGraphicsRectItem
{
Q_OBJECT
public:
NaviBar();
void setPageOffset(qreal ofs);
signals:
void pageSelected(int page);
protected:
void mousePressEvent(QGraphicsSceneMouseEvent *event);
void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = 0);
private:
QList<QGraphicsSvgItem*> m_icons;
QGraphicsRectItem *m_cursor;
};
函数实现
#define ICON_SIZE 50
#define ICON_PAD 4
NaviBar::NaviBar()
: QGraphicsRectItem()
{
setRect(0, 0, 5 * ICON_SIZE, ICON_SIZE);
setPen(Qt::NoPen);
QStringList names;
names << "map" << "web" << "home" << "weather" << "contacts";
for (int i = 0; i < names.count(); ++i) {
QString fname = names[i];
fname.prepend(":/icons/");
fname.append("-page.svg");
QGraphicsSvgItem *icon = new QGraphicsSvgItem(fname);
icon->setParentItem(this);
const int dim = ICON_SIZE - ICON_PAD * 2;
qreal sw = dim / icon->boundingRect().width();
qreal sh = dim / icon->boundingRect().height();
icon->setTransform(QTransform().scale(sw, sh));
icon->setZValue(2);
m_icons << icon;
}
m_cursor = new QGraphicsRectItem;
m_cursor->setParentItem(this);
m_cursor->setRect(0, 0, ICON_SIZE, ICON_SIZE);
m_cursor->setZValue(1);
m_cursor->setPen(Qt::NoPen);
m_cursor->setBrush(QColor(Qt::white));
m_cursor->setOpacity(0.6);
}
void NaviBar::setPageOffset(qreal ofs)
{
m_cursor->setPos(ofs * ICON_SIZE, 0);
for (int i = 0; i < m_icons.count(); ++i) {
int y = (i == static_cast<int>(ofs + 0.5)) ? ICON_PAD : ICON_PAD * 2;
m_icons[i]->setPos(i * ICON_SIZE + ICON_PAD, y);
m_icons[i]->setOpacity(1);
}
}
void NaviBar::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
emit pageSelected(static_cast<int>(event->pos().x() / ICON_SIZE));
}
void NaviBar::paint(QPainter * painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
painter->setBrush(Qt::white);
painter->setOpacity(0.2);
painter->drawRect(option->rect.adjusted(-20, ICON_PAD, 20, 0));
}
定义视图
class ParallaxHome: public QGraphicsView
{
Q_OBJECT
public:
QGraphicsScene m_scene;
NaviBar *m_naviBar;
QGraphicsPixmapItem *m_wallpaper;
QTimeLine m_pageAnimator;
qreal m_pageOffset;
QList<QGraphicsPixmapItem*> m_items;
QList<QPointF> m_positions;
public:
ParallaxHome(QWidget *parent = 0)
: QGraphicsView(parent)
, m_pageOffset(-2) {
setupScene();
setScene(&m_scene);
setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
setFrameShape(QFrame::NoFrame);
setWindowTitle("Parallax Home");
connect(&m_pageAnimator, SIGNAL(frameChanged(int)), SLOT(shiftPage(int)));
m_pageAnimator.setDuration(500);
m_pageAnimator.setFrameRange(0, 100);
m_pageAnimator.setCurveShape(QTimeLine::EaseInCurve);
pageChanged(static_cast<int>(m_pageOffset));
}
signals:
void pageChanged(int page);
public slots:
void slideRight() {
if (m_pageAnimator.state() != QTimeLine::NotRunning)
return;
int edge = -(m_pageOffset - 1);
if (edge < PAGE_COUNT)
slideBy(-1);
}
void slideLeft() {
if (m_pageAnimator.state() != QTimeLine::NotRunning)
return;
if (m_pageOffset < 0)
slideBy(1);
}
void slideBy(int dx) {
int start = m_pageOffset * 1000;
int end = (m_pageOffset + dx) * 1000;
m_pageAnimator.setFrameRange(start, end);
m_pageAnimator.start();
}
void choosePage(int page) {
if (m_pageAnimator.state() != QTimeLine::NotRunning)
return;
if (static_cast<int>(-m_pageOffset) == page)
return;
slideBy(-page - m_pageOffset);
}
private slots:
void shiftPage(int frame) {
int ww = width();
int hh = height() - m_naviBar->rect().height();
int oldPage = static_cast<int>(-m_pageOffset);
m_pageOffset = static_cast<qreal>(frame) / qreal(1000);
int newPage = static_cast<int>(-m_pageOffset);
m_naviBar->setPageOffset(-m_pageOffset);
if (oldPage != newPage)
emit pageChanged(newPage);
int ofs = m_pageOffset * ww;
for (int i = 0; i < m_items.count(); ++i) {
QPointF pos = m_positions[i];
QPointF xy(pos.x() * ww, pos.y() * hh);
m_items[i]->setPos(xy + QPointF(ofs, 0));
}
int center = m_wallpaper->pixmap().width() / 2;
const int parallax = 3;
int base = center - (ww / 2) - (PAGE_COUNT >> 1) * (ww / parallax);
int wofs = base - m_pageOffset * ww / parallax;
m_wallpaper->setPos(-wofs, 0);
}
protected:
void resizeEvent(QResizeEvent *event) {
Q_UNUSED(event);
layoutScene();
}
void keyPressEvent(QKeyEvent *event) {
if (event->key() == Qt::Key_Right)
slideRight();
if (event->key() == Qt::Key_Left)
slideLeft();
event->accept();
}
private:
void layoutScene() {
int ww = width();
int hh = height();
m_scene.setSceneRect(0, 0, PAGE_COUNT * ww - 1, hh - 1);
centerOn(ww / 2, hh / 2);
int nw = m_naviBar->rect().width();
int nh = m_naviBar->rect().height();
m_naviBar->setPos((ww - nw) / 2, hh - nh);
shiftPage(m_pageOffset * 1000);
}
void setupScene() {
qsrand(QTime::currentTime().second());
QStringList names;
names << "brownies" << "cookies" << "mussels" << "pizza" << "sushi";
names << "chocolate" << "fish" << "pasta" << "puding" << "trouts";
for (int i = 0; i < PAGE_COUNT * 2; ++i) {
QString fname = names[i];
fname.prepend(":/images/");
fname.append(".jpg");
QPixmap pixmap(fname);
pixmap = pixmap.scaledToWidth(200);
QGraphicsPixmapItem *item = m_scene.addPixmap(pixmap);
m_items << item;
qreal x = (i >> 1) + (qrand() % 30) / 100.0;
qreal y = (i & 1) / 2.0 + (qrand() % 20) / 100.0;
m_positions << QPointF(x, y);
item->setZValue(1);
}
m_naviBar = new NaviBar;
m_scene.addItem(m_naviBar);
m_naviBar->setZValue(2);
connect(m_naviBar, SIGNAL(pageSelected(int)), SLOT(choosePage(int)));
m_wallpaper = m_scene.addPixmap(QPixmap(":/icons/surfacing.png"));
m_wallpaper->setZValue(0);
m_scene.setItemIndexMethod(QGraphicsScene::NoIndex);
}
};
main函数
#include "parallaxhome.moc"
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
ParallaxHome w;
w.resize(360, 640);
w.show();
return app.exec();
}
效果图
作者：huihui1988
